Disk Utility Restore vs SuperDuper!

[dan]

Dave thanks for your replies.

I just completed a Disk Utility Restore of my internal hard drive to my external drive. I then checked the amount of used space on both drives:

Internal: 165 GB (177,169,125,376 bytes) boot drive
External: 161.53 GB (173,443,739,648 bytes)

I was not happy about the difference.

I then booted off of the external drive and checked the amount of used space:

Internal: 164.75 GB (176,897,163,264 bytes)
External: 164.78 GB (176,929,144,832 bytes) boot drive

but the initial amount of used space was 164.69 GB and over the span of a few minutes increased to 164.78 which I guess is because the amount of swap space used is increasing (even though I'm not doing anything). Am I in danger of not having the OS or an application work properly? Would the amount of used space been identical had I or if I used SuperDuper!? Thanks again for your answer!